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LCF Australia

Crop guide

Canola nutrition

Nutrient needs, growth stages, common deficiencies and why nutrients go missing in Australian canola.

Nutrient needs

Canola needs more nitrogen and much more sulphur than cereals for a similar yield. Sulphur is closely tied to how well the crop uses nitrogen, so the two are usually managed together.

Phosphorus at sowing supports early root growth. Boron matters for flowering and pod set on some soils. Canola seed is small and very sensitive to fertiliser placed with it.

Demand for both nitrogen and sulphur peaks between stem elongation and budding.

A flowering yellow canola crop filling the foreground and stretching to a flat horizon under a cloudy sky
Canola in flower. Photo: LCF Australia. This is a general crop photo, not a deficiency photo.

Key nutrients

Growth stages and when nutrients matter

  1. Stage 1

    Sowing and establishment

    The small seed is easily damaged by nitrogen and high fertiliser rates in the seed row. Phosphorus and some sulphur are commonly applied at sowing, often banded beside or below the seed.

  2. Stage 2

    Rosette

    Nitrogen and sulphur uptake builds as leaves develop. Early in-crop applications are often made during this stage.

  3. Stage 3

    Stem elongation (bolting) to budding

    The period of fastest nitrogen and sulphur uptake. Shortages here limit branching and flower numbers.

  4. Stage 4

    Flowering and pod fill

    Nutrients taken up earlier are moved into pods and seed. Boron and sulphur influence flowering and pod set.

Common deficiencies and signs

Symptoms of different problems can look alike. Disease, herbicide damage, waterlogging and frost can all produce signs similar to a deficiency.

Nutrient What to look for Where it is more likely
Sulphur Yellowing, cupped younger leaves, often with purple tints, then pale flowers and poor pod set. Sandy and low organic-matter soils, high-rainfall areas and paddocks with little recent sulphur.
Nitrogen Pale older leaves that may turn red or purple, and small, slow plants. Most soils, especially after cereals.
Phosphorus Small plants with dark or purplish leaves and slow early growth. Low-phosphorus soils and soils that tie up phosphorus.
Boron Distorted growing points, poor flowering and patchy pod set. Some sandy and acidic soils.

What deficiencies look like in canola

Photos of deficiency symptoms. Where we do not yet have a suitable photo, we will add our own trial photo. Symptoms vary with crop, variety, soil and season.

  • Sulphur deficiency in canola. We will add our own trial photo here.
  • Nitrogen deficiency in canola. We will add our own trial photo here.

Photos may show other crops with the same symptom. Full credits: Image credits.

Why nutrients go missing

Not everything applied to a canola crop ends up in it. These are the main ways nutrients are lost or become unavailable.

Sulphur and nitrogen imbalance
Canola needs sulphur to turn nitrogen into protein. When sulphur runs short, nitrogen taken up by the plant is used less fully, however much is available.
Leaching
Nitrate and sulphate dissolve in soil water and move down with it. On sandy soils, heavy rain can carry them below the root zone.
Volatilisation
Urea left on the soil surface is converted to ammonium and then to ammonia gas, which can escape to the air. The loss is greater on warm, moist soils with no follow-up rain, on alkaline soils and under heavy surface stubble.
Denitrification
When soil is waterlogged, oxygen runs short and soil bacteria convert nitrate into nitrous oxide and nitrogen gas, which are lost to the air.
Phosphorus fixation (lock-up)
Phosphorus reacts with calcium in alkaline soils, and with iron and aluminium in acidic soils, forming compounds plants cannot easily use. It also moves very little in soil. Calcareous soils and soils with a high phosphorus buffering index (PBI) bind more of it.
Seed-row effects
As urea dissolves next to the seed it releases ammonia, which can damage germinating seed. The effect is stronger with wider rows, narrower openers, sandy soils and dry seedbeds. Canola is among the most sensitive crops to fertiliser in the furrow.

LCF offers fertiliser technology matched to your use case, whether that is drilled urea or top dressing before or after planting. Advanced inhibitor technology is added in the compounding process at our manufacturing partner Lardmee (LDM).

How we match technology to your use case

How LCF products fit

LCF Australia supplies compound fertilisers made by our manufacturing partner Lardmee (LDM), including Urea Plus and zinc and manganese sulphates, on enquiry. We also supply the Field Spears soil testing kit, which reads soil N, P, K and pH in the paddock. Which product suits, how much and when depends on the soil, the crop, the season and how you apply it.